The expected costs of the Douglas sea wall scheme have spiralled by 80% since the project was first mooted.
Plans to build a 1.2m high sea wall from the war memorial to near the Empress Hotel on Central Promenade were submitted in September 2018.
At that time, the Department of Infrastructure said it expected the scheme to cost £500,000.
But now the project, which is due to get under way in January after revised plans were approved, is expected to cost in the region of £900,000.
A spokesman for the DoI said the costs of labour and material have increased dramatically in recent years.
He said the figure of £500,000 given in 2018 was when the best estimate prior to tender was £1,000 per linear metre.
The spokesman said: ‘The cost of materials and labour have increased dramatically in recent years, particularly steel, which will be used to reinforce the in-situ concrete and has increased 38% since 2022, and cement, which has witnessed a 40% increase in the past three years.’
The main aim of the wall is to reduce waves overtopping the highway, tram track and footways.
A revised planning application was submitted for the 500m-long reinforced concrete sea wall in 2019 after the earlier design was rejected by planners who said some people would be unable to see over the 1.2m (3ft 11ins) wall.
Despite the planning officer recommending approval, this, too, was refused by the planning committee which was still concerned at its detrimental and permanent impact on the conservation area and on public views of sea.
However, the application was then approved on appeal in May 2020.
The new wall will replace the existing railings along a 500m stretch of the Promenade from a point just south of the Douglas War Memorial on Harris Promenade to a point opposite the Empress Hotel on Central Promenade.
Following a formal tender process and Treasury approval, Island Drainage and Groundwork Ltd was appointed principal contractor.
Work to remove the existing railings and start construction of the new wall will begin in the latter part of January with the contractors expecting the project to be completed by the end of September 2024,
However, this time frame may be affected by weather conditions.
Public access past the work site will be maintained along the Promenade walkway.
It is intended that in the future this wall will form part of a wider response to climatic change and predicted sea level rises. The wall will be constructed from cast in-situ reinforced concrete with decorative surfaces that mirror the features on the existing concrete pillars.
To mitigate the loss of views out to sea, two viewing areas will be provided on the stepped landings just north of the Broadway and Loch Promenade side of the war memorial. These will have railings on the sea side with the rear of the landings (the wall line) capable of being closed off with flood boards as necessary.
The wall will be constructed to allow a for a future increase in the height of by up to 0.6m should it be necessary.
It will feature a series of artwork panels by local artists.
Existing access points to the beach will be maintained.
Planning approval has also been granted to replace a further section of railings between the Sea Terminal and the TT Café Kiosk next to the Bottleneck car park with a new sea wall.